Patent EP-4007107-A1 (EP)
Inventor: SHIGEMASA TAKASHI
IPC: H02J3/18
Filed: 2019-07-23
Abstract: A power conversion device is provided and connects a distributed power source to an electric power system connected to an infinite bus power system by converting electrical power of the distributed power source into alternating current power corresponding to the electric power system and by supplying the alternating current power after the converting to the electric power system; the power conversion device includes a major circuit part converting the electrical power of the distributed power source into the alternating current power corresponding to the electric power system, and a controller controlling an operation of the major circuit part; the controller includes an estimated value calculator, a reactive power calculator, and a drive circuit; the estimated value calculator calculates an estimated value of a resistance component of a system impedance of the electric power system, an estimated value of a reactance component of the system impedance, and an estimated value of a voltage value of the infinite bus power system based on an active power value of the connection point to the electric power system, a reactive power value of the connection point, and a voltage value of the connection point by using a Kalman filter applicable to a nonlinear equation; the reactive power calculator calculates a reactive power command value of reactive power supplied to the electric power system based on the estimated value of the resistance component of the system impedance, the estimated value of the reactance component of the system impedance, and the estimated value of the voltage value of the infinite bus power system; the drive circuit drives the major circuit part to output a prescribed active power and reactive power corresponding to the reactive power command value; the estimated value calculator includes a low-speed estimation calculator, a high-speed estimation calculator, and a control circuit; the low-speed estimation calculator calculates the estimated value of the resistance component of the system impedance, the estimated value of the reactance component of the system impedance, and the estimated value of the voltage value of the infinite bus power system; the high-speed estimation calculator calculates the estimated value of the resistance component of the system impedance, the estimated value of the reactance component of the system impedance, and the estimated value of the voltage value of the infinite bus power system by sampling the active power value, the reactive power value, and the voltage value of the connection point at a faster sampling rate than the low-speed estimation calculator; the control circuit selectively operates only one of the low-speed estimation calculator or the high-speed estimation calculator by controlling a switching of the low-speed estimation calculator and the high-speed estimation calculator; the low-speed estimation calculator and the high-speed estimation calculator calculate a predicted value of the voltage value of the connection point based on the estimated value of the resistance component of the system impedance, the estimated value of the reactance component of the system impedance, and the estimated value of the voltage value of the infinite bus power system and determine a prediction error of the voltage value of the connection point based on a measured value of the voltage value of the connection point and the predicted value of the voltage value of the connection point; the control circuit stops the operation of the low-speed estimation calculator and starts the operation of the high-speed estimation calculator when an absolute value of the prediction error input from the low-speed estimation calculator in a state of stopping the operation of the high-speed estimation calculator and operating the low-speed estimation calculator is greater than a first threshold, and stops the operation of the high-speed estimation calculator and starts the operation of the low-speed estimation calculator when the absolute value of the prediction error input from the high-speed estimation calculator in a state of stopping the operation of the low-speed estimation calculator and operating the high-speed estimation calculator is less than a second threshold less than the first threshold. Accordingly, a power conversion device and a distributed power source system are provided in which the voltage fluctuation of the connection point of a distributed power source can be suppressed more appropriately even when the fluctuation of the system characteristics is severe.